Auto balancing of (4) 24v 100Ah Lifep04 redodo batteries connected in series-parallel connections

[fabieville]

My battery bank have (4) 24v 100Ah batteries connected in 2P2S to give me 48V 200Ah. The manufacturer recommend i disassemble the pack and do a balancing every 6months.

Suppose I decide to get (2) 24V Lifepo4 charger and connect them.to each side of the series connection do u think it would charge each of them to 28.8v so that all batteries would be reading the same voltage whilst still connected in the parallel-series connection? This charging would take place once every couple months just to bring the SOC and voltage reading close as possible and i think i would let this occurs only when the outback mppt has reach 54.6v or near a full charge so basically when the charge controller reaches 54.6v and begins to float charge then the 2 chargers would commence charging of each side of the battery pack of so that there won't be any voltage difference between them or the most would be 0.01v at the end of the charge cycle. I would only do this when i notice a voltage difference between the 2 sides later on in the future as i don't expect to see it anytime soon because i have been using the batteries over 3 months now and the 2 sides are still showing the same voltage reading.

I would go with either a 1 or 2 Amp 28.8v Lifepo4 charger

Can this method work?

 

[sunshine_eggo]

Individually charging the 24V batteries in the bank will work; however, it may not be necessary. I trust that you individually and then in parallel charged all batteries to 28.8V for 2+ hours prior to wiring them 2S2P?

1) the individual 24V batteries need to be internally balanced. Charging only to 54.6V is unlikely to allow sufficient balance time. Recommend 55.2V for 2-3 hours with no tail current.

2) If you do #1, it is likely that the batteries will stay in balance.

If you observe that there is no more than 0.1V variation between the 24V batteries near the end of the absorption cycle, no balancing is required.

 

[fabieville]

I currently set my Outback MPPT charge controller to bulk charge to 55.2v with 20mins absorption time and also float charge at 55.2V Is this setting ok? Will this setting bring me close to 100% SOC and will the BMS able to balance the cells or do I need to increase the absorption time/Bulk Voltage? Do I need to set a lower float voltage?​

 

[sunshine_eggo]

I currently set my Outback MPPT charge controller to bulk charge to 55.2v with 20mins absorption time and also float charge at 55.2V Is this setting ok? Will this setting bring me close to 100% SOC and will the BMS able to balance the cells or do I need to increase the absorption time/Bulk Voltage? Do I need to set a lower float voltage?​

2 hours @ 55.2V
Float to 54V.

 

[fabieville]

My battery bank is a Redodo and I currently have (4) 24v 100Ah batteries string as 48v 200Ah 2P2S connection and the manufacturer told me this:

If you only charge it to 90% SOC， it is recommended voltage after 30 minutes of resting after charging is completed is: 13.6V-13.7V .
You are really right. The difference in batteries will get bigger and bigger during the use process, so it is recommended to balance them every 6 months for better protection and longer use time.

If you discharge them to 50% and then recharge them, the experience of using the batteries is very poor, it is recommended to discharge to 10%-20%, if 20%, the battery will have better lifespan and performance.​

With this info about is this really the case? I thought discharging only to 50 r 40% would give me more cycles? I didn't know that not going down to 20% would affect my performance and lifespan. Is this true because I don't see this online when i do a lot of research.

Also redodo states that their BMS starts balancing at 3.5v so with that case do i have to charge up to 56v each time or should i do a safe bulk charge of 55.2V and then maybe do a manually charge of each battery every 6months to the 56v or full charge voltage to get back all batteries internal cells in a balanced state and each batteries reading the same voltage before i reconnect them back in 2P2S?

 

[Johneb]

Fabieville, please stop shouting. I had to turn down my hearing aids.?

 

[Solar Newbee]

Fabieville, I have (4) Li Time 24v 200Ah batteries and wanted to connect them to make 48v 400Ah. You mentioned connecting them in 2P2S but what does that connection look like. Attached is the battery terminals , which I only have (2) 24v 200Ah connected for a 48v 200Ah running, but I don't have the other two 24v batteries connected yet. I'm just a little unsure of how to connect them all. Could you send a pic of the terminal connection of draw out a diagram? I know I can connect the second set in series and then connect it to the bus bar, it just means I have purchase for material, just trying to do it without buying any more material. Thank you

 

[Brucey]

If you discharge them to 50% and then recharge them, the experience of using the batteries is very poor, it is recommended to discharge to 10%-20%, if 20%, the battery will have better lifespan and performance.​

With this info about is this really the case? I thought discharging only to 50 r 40% would give me more cycles? I didn't know that not going down to 20% would affect my performance and lifespan. Is this true because I don't see this online when i do a lot of research.

I think they are talking about discharging to 50% when they are in series configuration. If they were being used singly then I doubt it would be a problem.

For an LFP battery you can use the whole capacity without any damage like a lead acid battery may encounter (where discharging to 50% capacity is common).